# Penetration depth below surface - Free Fall

• babbagero
In summary, the conversation discusses the scenario of an adult male free falling into the ocean at a high speed, with a discussion on the factors and numbers that can be estimated for the body. The main question posed is about the approximate depth at which the body would penetrate the surface, considering factors such as buoyancy and lung capacity. The conversation also mentions the use of specific dynamic modelling software for calculations, but notes that the coefficient of drag is a key unknown in this situation.
babbagero
So here is the scenario: an adult male 80kg, 6ft tall, slim build free falls into the open ocean feet first, hands locked into the groin. Speed at entry can be 200km/hr. We can assume the water is perfectly stile in reference to the surface tension. and for the body we can estimate some factors and numbers.. let's assume the body is prolate spheriod - completely rigid. not taking into account limbs flailing on impact and effecting ones drag on decent. Following entry the water trajectory during descent can be assumed in direct line with gravity. ones bouyancy can be assumed neutral or slightly negative. lung capactiy of 5.5 litres. My first question is at to what approximate depth would one calculate the body to penetrate the surface? (until the body has deaccelerated to a motion where the bouyancy is the only force relation) yes you could use specific dynamic modelling software, if anyone knows any good software let me know. I would like to see some estimated calculations first. If I have not stated any important information in my model please use a general value and state it in the reply. thanks Andy.

Have a look at this thread: https://www.physicsforums.com/showthread.php?t=627681 You could model your problem similarly. Note, however, that the biggest unknown in your situation is the coefficient of drag. I am not convinced that a prolate spheroid is a valid approximation here.

## 1. What factors affect the penetration depth below the surface during a free fall?

The main factors that affect the penetration depth below the surface during a free fall are the initial velocity, the angle of impact, the density and composition of the surface material, and the gravitational force.

## 2. How is the penetration depth below the surface calculated during a free fall?

The penetration depth below the surface can be calculated using the equation d = (v02sin2θ)/2g, where d is the depth, v0 is the initial velocity, θ is the angle of impact, and g is the gravitational force.

## 3. Is there a maximum depth that can be reached during a free fall?

Yes, there is a maximum depth that can be reached during a free fall. This is determined by the initial velocity, angle of impact, and the surface material. Once the object reaches its terminal velocity, it will stop accelerating and will not penetrate any further.

## 4. How does the density of the surface material affect the penetration depth below the surface?

The density of the surface material plays a significant role in determining the penetration depth below the surface. Objects with higher density will penetrate deeper than objects with lower density, assuming all other factors remain constant.

## 5. Are there any real-world applications for studying penetration depth below the surface during a free fall?

Yes, there are several real-world applications for studying penetration depth below the surface during a free fall. This is important in fields such as geology, where understanding the impact of objects on different types of surfaces can help in determining the composition and structure of the Earth's crust. It is also relevant in engineering, where the penetration depth can inform the design and safety of structures and materials subjected to impact forces.

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